Method for restricting heat transmission through a wall opening and air curtain

ABSTRACT

The invention relates to a method and air curtain for restricting heat transmission through a wall opening ( 120 ). Using the method according to the invention, an air curtain restricting heat transmission will be formed in front of the door opening. In the method on the first edge of the opening a blowing air flow going through a blow nozzle ( 12 ) is formed using a blower ( 20 ), and on the other edge of the opening a sucking air flow going through the suction opening ( 16 ) is formed. Advantageously the blowing air flow is formed at the lower edge of the opening and the sucking air flow at the upper edge of the opening. In this way, an air jet ( 40 ) will form in front of the door opening going from the blowing nozzle to the suction opening, and induced flows ( 42, 44 ) of air will form on both sides of the air jet, together forming an air curtain. The flowing of air through the door opening between the air jet and the vertical edges of the opening is reduced by side wallings ( 32 ). In the invention the induced air flow formed adjacent to the air jet is reversed back to the direction it came from in order to form a back flow ( 46 ) using an air deflector ( 30 ) placed on the other edge of the opening. The induced air flow and back flow form a circulating air flow alongside the air jet, with the temperature of the air mass being higher than the outside temperature. Because of the reduced temperature difference, the amount of heat moving through the opening is also reduced. Operation of the air curtain is controlled by an automatic control device ( 26 ).

FIELD OF INVENTION

The invention relates to a method for restricting heat transmission through a wall opening, such as a door opening, in which method on the first edge of the opening a blowing air flow going through a blow nozzle is formed and on the second edge of the opening a sucking air flow going through a suction opening is formed thereby forming an air curtain between the first edge and the second edge of the opening, said air curtain comprising an air jet moving from the blow nozzle to the suction opening and induced air flows formed on both sides of the air jet. The invention further relates to an air curtain operating according to the method.

BACKGROUND

Industrial and storage buildings, factory halls, workshops, vehicle garages, and the like, usually have large doors enabling vehicles to be driven inside the building. During times of the year when heating is needed, the opening of the door causes air flow where the warm inside air flows out of the building via the upper section of the door opening, while at the same time cold air flows into the building through the lower section of the door opening. Due to this air flow through the door opening, the need for heating energy for these spaces increases significantly. In addition, the air flows cause draughts and unstable and uneven temperature conditions indoors that have detrimental impacts on working conditions.

To reduce the air flow travelling through the door opening, methods has been developed where a controlled air flow parallel to the plane of the opening, so-called air curtain is created. This air curtain prevents, or at least restricts, the flow of air through the door opening. Such an air curtain is achieved by installing an intake channel on one edge of the opening, with an elongated blow nozzle running along the edge of the opening, through which air is blown into the opening. The other edge of the opening is fitted with an exhaust channel, with an elongated suction opening running along the edge of the opening for air intake. The intake and exhaust channels are linked with a connecting channel, inside of which there is a blower creating intake channel blow and exhaust channel suction. If necessary, the connecting channel may be fitted with a heater to warm the air. The direction of air flow for the air curtain may be adjusted with control plates fitted to the blow nozzle in order to prevent moving of the air curtain caused by pressure fluctuations, such as wind. This type of air curtain solution, where the blow nozzle is fitted to the upper edge of the opening, and the intake opening is located at the lower edge of the opening, is presented in the publication FI 35080. The placing of the blow nozzle and intake opening may also be reversed, or these may be installed to the opposing side edges.

Although significant energy savings and improved working conditions is achieved with known air curtains, it is clear that continual improvement of these characteristics is desired.

SUMMARY

An object of the invention is to provide an improved method for restricting heat transmission through a wall opening, and an air curtain functioning according to the method, where the positive characteristics of the air curtain mentioned above have been further improved and developed.

The objects of the invention are achieved with a method and air curtain, which are characterized by what is described in the independent claims. Some advantageous embodiments of the invention are described in the dependent claims.

The invention relates to a method and air curtain for restricting heat transmission through a wall opening. The invention may be used for example in places where there is a large outer door that needs to be opened frequently, e.g. for driving vehicles in or out. Using the method according to the invention, an air curtain restricting heat transmission will be formed in front of the door opening when the door covering the opening is in the open position. In the method on the first edge of the opening a blowing air flow going through a blow nozzle is formed, and on the other edge of the opening a sucking air flow going through the suction opening is formed. In this way, an air jet will form in front of the door opening going from the blowing nozzle to the suction opening. The air jet will also take the air within the immediate vicinity of the air curtain into the same directed motion, thereby forming induced flows of air on both sides of the air jet. The air jet and the induced air flows in combination form an air curtain. The basic idea of the method according to the invention is that the induced air flow formed adjacent to the air jet is reversed back to the direction it came from in order to form a back flow of air in the direction opposite to the direction of the air jet. The induced air flow and back flow form a circulating air flow alongside the air jet, with the temperature of the air mass being higher than the outside temperature, thereby reducing temperature differences between opposite sides of the air jet. Because of the reduced temperature difference, the amount of heat moving through the opening is also reduced.

In one preferred embodiment of the method according to the invention the induced air flow is reversed into back flow by installing an air deflector on the second edge of the opening.

In another preferred embodiment of the method according to the invention blowing air flow is formed on the lower edge of the opening and sucking air flow on the top edge of the opening.

In a third preferred embodiment of the method according to the invention flowing of air between the air jet and vertical edges of the opening is restricted by side wallings.

The air curtain according to the invention comprises an intake channel that has a blow nozzle for blowing air, arranged on the first edge of the opening, and an exhaust channel with a suction opening for the intake of air, arranged on the second, opposite edge of the first edge of the opening. The intake channel and exhaust channel are connected with a connecting channel, which has a blower therein for creating a blow in the intake channel and suction in the exhaust channel, and for forming an air jet between the blow nozzle and the suction opening. In addition, the air curtain comprises an air deflector arranged on the second edge of the opening for reversing the induced air flow formed alongside the air jet back to the direction it came from. The intake channel is advantageously installed to the lower edge of the opening, and the exhaust channel and the air deflector on the upper edge of the opening.

In one advantageous embodiment of the air curtain according to the invention the length of the blow nozzle of the intake channel and the length of the suction opening of the exhaust channel are substantially equal to width of the opening.

In another advantageous embodiment of the air curtain according to the invention the position of the blow nozzle of the intake channel is adjustable for directing the air jet to the desired direction.

A third advantageous embodiment of the air curtain according to the invention further comprises a control device for adjusting the position of the blow nozzle, for controlling blower operation, and for adjusting blowing power. Advantageously, the air curtain also comprises side wallings running along the vertical edges of the opening.

An advantage of this invention is that it prevents heat from escaping through an opening better than known air curtain solutions. Consequently the fluctuations in inside temperature are reduced and there will be less draught, thereby making it more pleasant and improving working conditions throughout the premises, in particular in spaces located close to the opening. Furthermore, by reducing the amount of heat escaping, savings will be made in the heating costs for the building.

BRIEF DESCRIPTION OF THE DRAWINGS

The following paragraphs describe the invention in detail. The description refers to the attached drawings, where

FIG. 1 a shows by way of example of an air curtain according to invention, pictured from the front; and

FIG. 1 b shows a cross-section of the air curtain depicted in FIG. 1 a.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1 a and 1 b show by way of example an air curtain according to the invention that employs the method according to the invention. FIG. 1 a depicts the air curtain from the front, and FIG. 1 b shows a cross-section of the same air curtain. The air curtain according to the invention is installed to the wall 100 of the building, in front of the door opening 120. An openable bascule door 140 is installed to the inner side of the door opening.

The air curtain of the invention has an intake channel 10 running alongside the lower edge of the door opening, which is embedded in a hollow 22 placed in front of the door opening. The open top section of the hollow is covered with grating 24, which enables unobstructed driving or walking over the hollow. The structure of the grating has been designed not to prevent air from flowing through the grating. On the edge facing upwards from the intake channel is a blow nozzle 12 that substantially covers the complete width of the door opening.

The upper edge of the door opening has an exhaust channel 14 running along the edge, with the lower edge housing a suction opening 16 that substantially covers the complete width of the door opening. Near one vertical edge of the door opening is a vertical connecting channel 18, the first end of which is connected to the end of the intake channel, and the other end connected to the end of the exhaust channel. Inside the connecting channel there is an electrically operated blower 20 which, when operated, forms a sucking air flow into the exhaust channel and a blowing air flow into the intake channel. Operation of the blower is controlled by an automatic control device 26.

The air curtain of the invention further includes a protective hood 28 installed above the door opening that covers substantially the entire width of the door opening and has a vertical front walling. To the underside of the protective hood an air deflector 30 has been formed. The air deflector is a formed, trough shaped part, which is positioned parallel to the direction of the upper edge of the door opening with the first edge placed close to the plane defined by the outer edge of the intake channel and the outer edge of the exhaust channel, and the second edge is placed close to the front walling of the protective hood. Advantageously the height of the cross-section of the air deflector is 100-1000 mm and the width is 500-2000 mm. The second edge of the air deflector has a substantially vertical fringe area, the width of which is advantageously 50-500 mm. The edges of the air deflector are installed substantially at the same height level as the lower surface of the exhaust channel. Further, along both vertical edges of the door opening there are side wallings 32 protruding from the outer wall at substantially right angles. The side wallings run from the ground level to the protective hood, and their reach measured from the surface of the outside wall is advantageously 500-1500 mm. The length of the air deflector is substantially the same as the distance between the side walling of the first vertical edge of the door opening and the side walling of the second vertical edge of the door opening.

The air curtain of the invention operates in the following way: When the blower 20 is switched on, air begins to flow from the intake channel 10 via the blow nozzle 12 to the door opening 120. In this way a maintainable directed air jet 40 is formed in front of the door opening. At the same time, air is sucked through the suction opening 16 to the exhaust channel 14. The air jet 40 blown from the blow nozzle is directed as effectively as possible towards the suction opening. The direction of the air jet may be adjusted as required by turning the position of the blow nozzle, either towards the wall 100 or away from the wall. The flow velocity of the air jet may also be adjusted by altering the blower power. By adjusting the air jet direction and flow velocity, the air jet may always be as effectively as possible directed to the suction opening, despite fluctuations in pressure differences on different sides of the door opening. Side wallings 32 prevent air from flowing through the door opening between the vertical edges of the door opening and air jet.

The air jet blown from the blow nozzle will take the nearby air mass into the same directed motion; thereby forming induced air flows on both sides of the air jet. The innermost induced air flow 42 is formed with the building's indoor air mass, i.e. indoor air, and the outermost induced air flow 44 is formed with the outdoor air mass, i.e. outdoor air. It is clear that some mixing of air masses will occur between the induced air flows and the air jet, where heat moves from warmer air mass to colder. In wintry conditions this means that the heat of the indoor air will move from the innermost induced air flow 42 to the air jet 40, and from thereon to the outermost induced air flow 44. The induced air flows parallel to the direction of air jet form localised low pressures around the lower edge of the door opening on both sides of the air jet. These low pressures will form streams horizontally travelling towards the door opening; indoor stream A and outdoor stream B.

In the air curtain according to the invention the outermost induced air flow 44, adjacent to the air jet, is directed to the air deflector 30 next to the suction opening 16. The induced air flow reaches the first edge of the air deflector, flows round the curved, trough-like hood and exits the air deflector via the other edge. The other edge of the air deflector has a substantially vertical fringe area, which directs the air flow exiting the air deflector substantially vertically downwards. In other words, the air deflector reverses upwardly moving induced air flow into downwardly moving back flow 46. The air mass constituting the back flow flows downwards to the ground where it joins to the horizontal stream B to then join the new induced flow. Thus in the air curtain according to the invention, a circulating air flow is formed adjacent to the air jet 40 achieved by of the blow nozzle, which circulating air flow remains in the space defined by the air deflector and the side wallings 32. As the outermost induced air flow is continually met with heat from the indoor air, the back flow temperature is higher than the outdoor temperature. Using the invention the temperature of the air mass in the immediate proximity of the outside door opening is thus raised.

Operation of the air curtain in the invention is controlled with an automatic control device 26 that automatically adjusts the direction of the air jet and flow velocity in accordance with prevailing conditions in the environment. The control device automatically switches on the blower 20 of the air curtain when the sensors of the control device (not illustrated) sense that the door 140 of the door opening is in the open position. Similarly the control device switches the blower off automatically when the door is shut.

The method and air curtain according to the invention are especially suitable for using in cold climatic areas, where the loss of heat through an open door opening can be significantly reduced by them. The method and door curtain according to the invention may, however, also be applied for use in warmer conditions where the outdoor temperature is higher than inside the building. In this way the invention can reduce the transmission of heat through the door opening into the building, thereby reducing the amount of energy required for cooling indoor air.

The visible structures of the air curtain according to the invention, such as the protective hood 28, connecting channel 18 and side wallings 32, may be made in accordance with the requirements of each individual site. The protective hood and side wallings may, for example be constructed as fixed sections of the building's facade. The structures may also be placed on the inner side of the door opening, and they may be used inside the building in the openings of dividing walls between departments.

Some advantageous embodiments of the method and air curtain according to the invention were described above. The invention is not limited to the solutions described above, but the inventive idea can be applied in numerous ways within the scope defined by the claims. 

1. A method for restricting heat transmission through a wall opening, such as a door opening, in which method on the first edge of the opening a blowing air flow going through a blow nozzle is formed and on the second edge on the opening a sucking air flow going through a suction opening is formed, thereby forming an air curtain between the first and second edge of the opening, said air curtain comprising an air jet moving from the blow nozzle to the suction opening and induced air flows formed on both sides of the air jet, wherein the induced air flow formed alongside the air jet is reversed back to the direction it came from to form a back flow having a flow direction opposite to the flow direction on the air jet.
 2. A method according to claim 1, wherein the induced air flow is reversed into back flow by arranging an air deflector on the second edge of the opening for deflecting the direction of induced air flow.
 3. A method according to claim 1, wherein the blowing air flow is formed at the lower edge of the opening and sucking air flow at the upper edge of the opening.
 4. A method according to claim 1, wherein flowing of air between the air jet and vertical edges of the opening is restricted with side wallings.
 5. An air curtain to be formed in front of a building's wall opening, such as a door opening, comprising an intake channel, having a blow nozzle for blowing air, to be arranged on the first edge of the opening, an exhaust channel, having a suction opening for sucking air in, to be arranged on the second edge, opposing to the first edge of the opening, a connecting channel connecting the intake channel and exhaust channel, and a blower to be located in the connecting channel for forming an air jet between the blow nozzle and suction opening and an air deflector to be arranged on the second edge of the opening for reversing the induced air flow formed alongside the air jet back to the direction from which it came.
 6. An air curtain according to claim 5, wherein the intake channel is arranged to the lower edge of the opening and the exhaust channel and air deflector are arranged to the upper edge of the opening.
 7. An air curtain according to claim 5, wherein the length of the blow nozzle of the intake channel and the length of the suction opening of the exhaust channel are substantially equal to the complete width of the opening.
 8. An air curtain according to claim 5, wherein the position of the blow nozzle of the intake channel is adjustable for directing the air jet to the desired direction.
 9. An air curtain according to claim 5, wherein it further comprises side wallings along the vertical side edges of the opening.
 10. An air curtain according to claim 5, wherein it further comprises a control device for adjusting the position of the blow nozzle, for controlling the functioning of the blower and for controlling the blowing power of the blower. 